> -----Original Message-----
> From: PIC microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Gavin Jackson
> Sent: March 14, 1998 00:42
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Power Supply
>
>
> Hi there once again
>
> Correct me if I'm wrong, but I though that the 78XX voltage
> regulators can only take 3X the output voltage on their input,
> so the maximum supply that a 7805 can have as its input
> is 15V.

        Not as far as I know, I believe the whole 78XX series has a common max
voltage, around 35V if memory serves, You can check the data sheets if you
want, I believe NS has them online for that product...
Excerpt from LM7805C datasheet, page 2:

Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Input Voltage (V O e 5V, 12V and 15V) 35V
Internal Power Dissipation (Note 1) Internally Limited
Operating Temperature Range (T A ) 0 'C to a70 'C
Maximum Junction Temperature
(K Package) 150 'C
(T Package) 150 'C
Storage Temperature Range b65 'C to a150 'C
Lead Temperature (Soldering, 10 sec.)
TO-3 Package K 300 'C
TO-220 Package T 230 'C

TTYL